1. Field of the Invention
The invention relates to superconducting electromechanical rotating (SER) devices and, more particularly relates to an SER device having a stator assembly including a stator winding which is potted to an associated support. The invention additionally relates to a method of potting a stator winding of an SER device to the associated support.
2. Discussion of the Related Art
Recent advances in superconductivity have led to an increased interest in the development and commercialization of superconducting electromechanical rotating (SER) devices such as large electric generators and large electric motors including synchronous AC motors. The device includes a superconductive rotor having a vacuum jacket and a stator coaxially surrounding the rotor. The superconducting coils are disposed inside of the vacuum jacket on a coil support structure. The coil support structure and coils are cooled to a cryogenic temperature. One such device is the so-called high temperature superconducting (HTS) electromechanical device which uses a HTS winding in the rotor of the device rather than a low temperature superconducting winding. In the case of a synchronous AC motor, the stator and rotor of the typical SER device are configured such that the rotor is rotated synchronously by the rotating stator magnetic field.
The usual stator of an SER device consists of a winding formed from coils that are mounted in axially extending, peripherally-spaced slots in the inner radial surface of a support structure of the device and that are held in place by fixturing straight portions of the winding to the slots and by mechanical hangers and/or rope or fabric in the end winding areas. Because the SER device operates at a much higher magnetic flux level than other machines, it typically does not have magnetic teeth. Such a machine is referred to as an "air core" machine. In an air core machine, the hypothetical ideal stator would have 100% of the space between the back-iron and the rotor filled with copper. However, in practice, practical limitations are imposed on the copper content of an SER device. These practical limitations include the insulation thickness, the end winding length, the need to cool the winding, and coil manufacturing issues. These practical limitations represent a problem in SER stator winding design.
The usual stator winding topology used in SER devices is not the optimal solution to this problem. The usual stator winding has a so-called two-layer topology in which 1) the number of coils equals the number of slots in the support surface on which the stator winding is mounted and 2) each slot contains one section of two different coils. Windings having a two-layer topology require relatively long end windings. This problem is exacerbated if the gap between adjacent straight portions of the coils is decreased in an effort to increase the total effective copper content of the device because, as the gap is decreased, the end winding length is increased proportionally, theoretically tending to infinity when the gap tends to zero.
Another problem-associated with usual SER stator winding designs is that they are relatively difficult to mount on the support structure. The usual stator winding is formed from a plurality of coils inserted into the slots in the inner radial surface of the support structure. The stator winding is then fixed in the slots using topsticks at the straight sections of the coils and mechanical fasteners such as hangers and/or fabric or rope at the end winding areas. This mounting technique is cumbersome and highly labor-intensive. Stator winding mounting becomes increasingly difficult as the space between adjacent straight portions of the stator coils is progressively decreased in an effort to increase copper content and current density. In fact, at one point, further gap reduction, even if not precluded by cooling constraints or other constraints, is precluded by the physical spacing required to receive the mechanical fasteners between coil portions.